Although the attributed cause is indeed what was behind the reported problem, and although one can take advantage of Vista's support of Unicode 5.0 as I stated, there is another solution that can work here for a wider range of cases.

One can actually take advantage of normalization in this case -- taking inspiration from the current state of the City Elders long past, you can decompose the Greek text to help out here.

You see, it goes something like this (using Richard's example of U+1F96, rendering support may vary for you depending on all sorts of OS/browser/font issues):

ᾖU+1f96 (GREEK SMALL LETTER ETA WITH PSILI AND PERISPOMENI AND YPOGEGRAMMENI) decomposes to:

Now obviously this will not work for characters using scripts in Unicode that versions of Windows prior to Vista don't handle at all, like Tibetan or Mongolian. But Greek has worked for a long time, and Unicode Normalization gives a solution to the problem that will work quite well in Microsoft and third party products not yet running on Vista! :-)

This post brought to you byᾖ(U+1f96, a.k.a. GREEK SMALL LETTER ETA WITH PSILI AND PERISPOMENI AND YPOGEGRAMMENI)